feat: add optional geoData property as alternative to geofile

[dpraul]

Hi again!

We need to use d3-geomap in an environment where fetch is not available, and we already have the TopoJSON contents loaded on the page, so I've added the geoData key as an alternative to geofile.

You can pass the TopoJSON contents in directly to the geoData property. In doing so, the geofile property is ignored, and fetch becomes an optional dependency. No other functionality should be affected.

I also added some inline docs for clarity :)

[yaph]

Thanks for adding this useful feature.

[dpraul]

thanks for merging this so quickly! do you intend to do a release anytime soon?

[yaph]

Yes, not sure yet if this week or beginning of next week.

[yaph]

New release is out.

[dpraul]

Thank you!